1. Field of the Invention
The invention relates to a plasma display device, and more particularly to a plasma display device having uniform barrier ribs.
2. Description of the Related Art
Recently, flat panel displays, such as liquid crystal displays and plasma displays, become to replace traditional cathode ray tube displays. The plasma display is a flat panel displaying images by discharging gas, with lighter weight and thinner volume, a large viewable area, and no viewing-angle restriction.
The plasma display includes a front panel and a back panel, and a plurality of barrier ribs are formed on the back panel. These barrier ribs in the plasma display can be formed by a screen-printing method and/or a sandblasting method. These barrier ribs with different heights cause a serious problem. For example, a height difference between the highest and lowest barrier ribs is about 10 xcexcm, so that the highest barrier rib is easily cracked or broken because of the pressure formed during the assembly process of the front panel to the back panel.
A discharge display device is disclosed in U.S. Pat. No. 5,754,003. Referring to FIG. 6, a plurality of height adjusting layers 32 are formed on the front panel 101. These height adjusting layers 32 are corresponded with these barrier ribs 103. Each height adjusting layer 32 is made of a material having a low softening temperature. However, it is not easy to control the amount of the height adjusting layers 32, and some of the height adjusting layers 32 may overflow onto the phosphor layer 104 on the rear panel 102 at high temperatures, causing defects of the display.
To solve the above problems, it is an object of the present invention to provide a plasma display device to solve the problem of the height difference among the barrier ribs.
According to the object mentioned above, the present invention provides a plasma display device having a first panel and a second panel parallel to each other. A first dielectric layer is formed on the second panel, a plurality of barrier ribs are formed on the first dielectric layer, and a plurality of buffer layers are formed opposite to the barrier ribs. The buffer layers have a first softening temperature, the barrier ribs have a second softening temperature, and the first softening temperature is lower than the second softening temperature. The buffer layers can be deformed and compressed at a temperature higher than the first softening temperature during a process for sealing the first and second panels, so as to unify heights of the barrier ribs.
Each buffer layer can be disposed in the middle of each barrier rib or between the first dielectric layer and each barrier rib. Moreover, the width of each buffer layer is preferably not larger than the width of each barrier rib. Thus, the buffer layer has enough space to expand during a sealing process of the first panel and the second panel. The buffer layer will not easily overflow onto the phosphor layer of the plasma display device to produce defects.
Furthermore, the difference between the first softening temperature of the buffer layer and the second softening temperature of the barrier rib is about 20xc2x0 C. to 100xc2x0 C., and preferably about 20xc2x0 C. to 30xc2x0 C.
The material of the buffer layer is a mixture of oxide, such as a mixture of Bi2O3, Li2O, Na2O, CaO, . . . etc.
According to the present invention, the buffer layers can be formed on the first panel. A second dielectric layer is further formed on the first panel to cover the buffer layers. The dielectric layer includes a plurality of concave portions, and positions of the concave portions are corresponded with positions of the buffer layers. A protecting layer can be formed on the second dielectric layer.
According to the present invention, the buffer layers can be formed above the second dielectric layer, and the protecting layer can be formed to cover the buffer layers.